Analysis of a severe storm in southwest Anhui on 29 April 2013 based on radar data

A severe storm occurred at Anqing City and Dongzhi County on 29 April 2013. The radar echo characteristics and the evolution of physical parameters of the storm cell were analysed based on Jiujiang radar data and ancillary data from GFS forecast fields and surface conventional observations the results are as follows. ⑴ Radar reflectivity indicates that the severe storm has a vortex-shaped echo. High reflectivity gradient area was observed in front of the vortex-shaped echo. The fact that the vortex-shaped area in the velocity map had a continuous mesoscale cyclonic flow indicates that the severe storm was a supercell storm. The top of the severe storm was taller than 11 km, above the -20 ℃ level height, which is considered to be an important indicator for the storm to produce large hails. ⑵ Based on storm and meso-cyclone parameters, hails occurred when the height of the maximum reflectivity (HT) and the storm top height (TOP) were increased to their peak values. The maximum vertically integrated liquid water (VIL) was 58 kg·m-2, and the maximum reflectivity (DBZM) was 77 dBz. The VIL density (DVIL) with value greater than 4.0 g·m-3 lasted for more than 1 hour, and its maximum reached over 6.0 g·m-3. ⑶ In this severe storm case, large hails occurred half hour after the maximum DVIL was observed, where DVIL had the largest gradient with a value of 5.0 g·m-3. Strong wind was found when the meso-cyclone persisted relatively long in duration and high in altitude.